JPH11161429A - Coordinate measuring instrument of touch panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a measuring speed with simple constitution by providing a circuit switching means which switches two electrodes of the touch panel and a comparator which has its output inverted according to a specific threshold value and using a keying wait state even as an x-coordinate measurement state. SOLUTION: Keying detection is abolished and x-coordinate measuring operation or y-coordinate measuring operation is used in common. The threshold voltage Vth of the comparator IC 3 is set between the signal voltage at the time of coordinate keying and 0 V. An analog switch ASW2 is placed in only two open and grounding states. The outputs of diode limiters D1 and D3 are connected to the signal of a yU electrode through a diode D3 and a diving resistance R8. Thus, the analog switches ASW1 to ASW4 which perform circuit switching of the electrodes xL and xR, and yU and yL of the touch panel and the comparator IC3 which has its output inverted according to the specific threshold value are provided and the key wait state is used even as the x- or y-coordinate measurement state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digitizer, and more particularly to a coordinate measuring device for an analog touch panel.

[0002]

2. Description of the Related Art Conventionally, touch panels have been widely used in various information processing devices as small input devices.
First, the configuration and operation of a conventional analog touch panel will be described with reference to the drawings.

FIG. 2 is a perspective view showing an example of a schematic structure of a conventional analog touch panel. In the figure, 1 is a film substrate, 2 is a Y transparent conductive film, 3 is a glass substrate, 4 is an X transparent conductive film, 5 is a spacer, xL is x
L electrode, xR is xR electrode, yU is yU electrode, yL is yL
2 shows an electrode.

[0004] As shown in FIG.
It has two transparent conductive films 2 and 4 having a certain finite resistance value. At least one of the transparent conductive films 2 and 4 is formed on a flexible base material.
, A Y transparent conductive film 2 is provided. And this Y
At the end of the transparent conductive film 2, a yU electrode and a yL electrode are attached as detection electrodes (U is on the upper side and L is on the lower side). In the case of FIG. 2, the other transparent conductive film (IT
O), that is, the X transparent conductive film 4 is formed on the upper surface of the glass substrate 3 (the side facing the Y transparent conductive film 2).

[0005] At the end of the X transparent conductive film 4, an xL electrode and an xR electrode are attached as electrodes for detection (L is left side, R is right side). In order to maintain a small space between the films facing the transparent conductive films 2 and 4,
For example, a spacer 5 having a height of about 3 to 10 μm is provided. This touch panel is usually some kind of display device,
For example, used in combination with a liquid crystal display device LCD, etc.
By pressing the keying surface according to the display, the coordinate position is input, and a predetermined operation is performed.

FIG. 3 is a schematic side view for explaining a deformation state of the touch panel shown in FIG. 2 during operation, wherein (1) shows a state of waiting for key tapping, and (2) shows a state of pressing down a key tapping surface. .
The reference numerals in the figure are the same as those in FIG. 2, and the arrow A indicates the pressing direction.

[0007] The key touching surface is indicated by an arrow A using a fingertip of a person or a pen.
When pressed in the direction shown in FIG. 3, as shown in FIG.
Comrades come in contact. Conversely, when the pressing force is removed (the fingertip, the pen or the like is released), the shape of the film substrate 1 which is a flexible substrate is restored, and as shown in FIG. , 4 return to the non-contact state.

FIG. 4 is a functional block diagram showing an example of a keying position detecting circuit for detecting a keying position of the touch panel shown in FIG. The reference numerals in the figure are the same as those in FIG. 2, 6 is a touch panel, IC1 and IC2 are voltage followers, IC
3 is a comparator, IC4 is an A / D converter (analog /
Digital converter), LPF1 and LPF2 are low-pass filters, ASW1 to ASW4 are analog switches, S0 and S1 are each terminal of analog switch ASW2, D1 and D2
Represents a diode, R1 to R7 represent resistors, C1 and C2 represent capacitors, and Vth represents a threshold voltage of the comparator IC3.

The keying position detecting circuit shown in FIG. 4 has a function of detecting the keying position of the touch panel shown in FIG. 2 as an electric signal. The touch panel 6 has, in an equivalent circuit thereof, two pairs of electrodes x of the touch panel orthogonal to each other.
L, xR (hereinafter referred to as xL electrode and xR electrode as appropriate)
The electrodes yU and yL (hereinafter, appropriately referred to as yU electrodes and yL electrodes) are provided. And one set of xL,
Analog switches ASW2, ASW
SW4 is connected. Similarly, the other set of yU,
The analog switches ASW1, ASW1
SW3 is connected.

First, in the state of waiting for key input, the analog switches ASW1 and ASW3 are open. The analog switch ASW2 is in a state where the terminal S0 is closed, and the analog switch ASW4 is in a closed state. That is,
The xL and xR electrodes are held at a constant potential, and the yU and
Since the analog switches ASW1 and ASW3 of the yL electrode are open, the potential is guided to the comparator IC3 and the voltage follower IC2 via the load resistor R3 and the low-pass filter LPF1. When a key is pressed in this state, the potential of the X transparent conductive film (4 in FIG. 2) is transmitted to the Y transparent conductive film (2 in FIG. 2) through the contact portion and transmitted to the input of the comparator IC3. Since the threshold voltage Vth (approximately 3 V) of the comparator IC3 is set to about half of the bias voltage of the touch panel 6, the comparator I3
C3 is inverted to generate a keystroke signal. Here, the diodes D1 and D2 function as limiters. When the analog switch ASW2 is switched to the terminal S1 after the generation of the keying signal, the x signal output from the voltage follower IC2 has a potential proportional to n, which is the division ratio of the resistor R1. When this x signal is A / D converted (analog / digital converted) by the A / D converter IC4, x
The coordinates are determined.

Next, the analog switches ASW1 and ASW
3 is closed and the analog switches ASW2 and ASW4 are opened, the y signal output from the voltage follower IC1 has a potential proportional to m. That is, the potential becomes proportional to the y-coordinate. When the y-signal is A / D-converted, the y-coordinate is obtained. As described above, the conventional analog touch panel measures the x and y coordinates by performing a three-stage operation of keying detection → x coordinate measurement → y coordinate measurement. To read coordinates continuously,
By repeating the above operation, the measurement can be continuously performed.

[0012]

As described in the prior art, in order to measure the x and y coordinates, it is necessary to detect keying →
It is necessary to go through three states of x coordinate measurement → y coordinate measurement. On the other hand, the time required for the measurement is limited by the response time of the low-pass filter LPF1 formed by the resistor R4 and the capacitor C1. This low-pass filter LPF1
Is added to reduce noise induced from a display device (for example, a liquid crystal display device LCD) used in combination with an analog touch panel. The response time of the low-pass filter LPF1 is represented by a time constant. However, a stable signal usually requires three times or more the time constant, which hinders high-speed operation.

Usually, this time requires, for example, about 5 msec. Therefore, the time required for measuring the x and y coordinates is about 15 msec including the keying detection, and is about 67 msec.
A sampling rate of samples / second results. This speed is
It cannot be said that the speed is high enough for practical use, and a method of sampling at high speed is desired. SUMMARY OF THE INVENTION It is an object of the present invention to provide a touch panel coordinate measuring device that can improve the measuring speed with a simple configuration.

[0014]

According to the first aspect of the present invention, one or both of opposingly disposed flexible substrates and a conductive film having a finite electric resistance formed inside the substrates, respectively. And two sets of touch panel electrodes xL and xR and touch panel electrodes yU and yL formed at the ends of the respective conductive films and orthogonal to each other, and an insulating spacer between the two base materials. Circuit switching means for switching the circuits of the two sets of electrodes xL, xR and electrodes yU, yL, and a comparator whose output is inverted by a predetermined threshold value, so that the key tapping wait state is also used as the x coordinate measurement state. I have to.

According to a second aspect of the present invention, in the coordinate measuring device of the first aspect, the comparator output is connected to the touch panel electrode xL or the electrode xR via a diode switch and a damping resistor to stabilize the keying detection characteristic.

According to a third aspect of the present invention, in the coordinate measuring device of the first aspect, the comparator output is connected to the touch panel electrode xL or the electrode xR via a diode switch and a damping resistor to lower the potential of the electrode xL or the electrode xR. This improves the noise margin with respect to the threshold value of the comparator.

According to the fourth aspect of the present invention, one or both of the opposing ones are a flexible base material, a conductive film having a finite electric resistance formed inside the base material, and the respective conductive films. And two sets of touch panel electrodes xL and xR and a touch panel electrode y which are formed at right angles to each other.
In a touch panel including U, yL and an insulating spacer between two substrates, a circuit switching means for switching a circuit between two sets of electrodes xL, xR and electrodes yU, yL of the touch panel, and a predetermined threshold A comparator whose output is inverted depending on the value is provided so that the key input waiting state is also used as the y coordinate measurement state.

According to a fifth aspect of the present invention, in the coordinate measuring apparatus of the fourth aspect, the comparator output is connected to the touch panel electrode yU or the electrode yL via a diode switch and a damping resistor to stabilize the keying detection characteristic.

According to a sixth aspect of the present invention, in the coordinate measuring device of the fourth aspect, the comparator output is connected to the touch panel electrode yU or the electrode yL via a diode switch and a damping resistor to lower the potential of the electrode yU or the electrode yL. This improves the noise margin with respect to the threshold value of the comparator.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a coordinate measuring apparatus according to the present invention, the number of states is reduced from the conventional three states to two states.
The feature is that the coordinate measuring speed is improved (the inventions of claims 1 and 4). Also, the comparator output is connected to the electrode x via a diode switch and a damping resistor.
It is connected to L or the electrode xR to stabilize the keying detection characteristic (the invention of claims 2 and 5). Furthermore, the output of the comparator is connected to the electrode xL or the electrode xR via a diode switch and a damping resistor so that the potential of the electrode xL or the electrode xR can be lowered so as to be separated from the threshold potential. 3 and the invention of claim 6).

FIG. 1 is a functional block diagram showing an example of an embodiment of a keying position detecting circuit for detecting a keying position on a touch panel in the coordinate measuring device of the present invention. The reference numerals in the figure are the same as those in FIG. 4, where D3 is a diode and R8 is a damping resistor.

The coordinate measuring apparatus of the present invention shown in FIG. 1 is different from the conventional coordinate measuring apparatus shown in FIG. 4 in the following four points. First, key detection is abolished, and the x-coordinate measurement operation or the y-coordinate measurement operation is also used (the invention of claims 1 and 4). Second, the threshold voltage Vth of the comparator IC3 is set to 0 V with the signal voltage at the time of keying the coordinates (0, 0).
Set between. Third, the analog switch ASW2
Conventionally, three states of +5 V, open and ground are taken, but in the present invention, there are only two states of open and ground. Fourth,
The outputs of the diode limiters D1 and D2 are
3 and the signal of the yU electrode through the damping resistor R8 (the inventions of claims 2 and 3 and claims 5 and 6).

Next, the operation of the coordinate measuring device shown in FIG. 1 will be described. The key tapping wait state is the same as the x coordinate measurement state. That is, the analog switch ASW2
Is connected to the terminal S1 and the analog switch ASW4
Is closed. Also, the other analog switch ASW
1, ASW3 is open. In this state, the yU electrode is at the ground potential, and the output of the comparator IC3 is negative. Therefore, the limiter diode D2 is in a conductive state and has a potential of about -0.6V. At this potential, the diode D3 also becomes conductive, and the load resistance of the yU electrode becomes the parallel combined resistance of the resistors R3 and R8.

Next, when the key is hit, the potential of the yU electrode rises, but the rise is damped by the resistor R8. However, the potential of the yU electrode continues to rise further, and the threshold value Vth of the comparator IC3 (コ ン パ レ ー タ 0.5 V)
Is exceeded, the comparator IC3 is inverted, an interrupt signal is given to the A / D converter IC4, the diode switch D3 is cut off, and the damping resistor R8 is disconnected. Since this state is the x coordinate measurement state, after waiting for the bounce chattering time, A / D conversion is performed to measure the x coordinate (the inventions of claims 2 and 5).

Then, one analog switch ASW
1, ASW3 is closed and the other analog switch ASW
2. Open ASW4. Since this state is a y-coordinate measurement state, after waiting for the response time of the low-pass filter LPF2, A / D conversion is performed to measure the y-coordinate.
Thereafter, the state returns to the x coordinate measurement state again. If the key input has been continued, the comparator IC3 continues to output the key input detection signal as it is. However, when the key input is completed, the potential of the yU electrode returns to the ground potential, and the comparator IC3 is also inverted. The generation of the tap signal is also stopped.

As described above, in the coordinate measuring apparatus for a touch panel according to the present invention, two pairs of electrodes xL and x of the touch panel are provided.
Circuit switching means (analog switches ASW1 to ASW4) for performing circuit switching of R and electrodes yU and yL;
A comparator (comparator IC3), whose output is inverted by a predetermined threshold value, is provided so that the key input waiting state is also used as the x coordinate measurement state. Thus, by reducing the number of states from the conventional three states to two states,
The coordinate measurement speed can be improved (the invention of claim 1). Further, since the key input waiting state can be used also as the y coordinate measurement state, the coordinate measurement speed can be similarly improved (the invention of claim 2).

[0027]

According to the coordinate measuring apparatus for a touch panel of the first aspect, the keying detection → x coordinate measurement →
The x-coordinate and the y-coordinate can be measured in two steps of x-coordinate measurement (key detection) → y-coordinate measurement instead of three steps of y-coordinate measurement. Therefore, the measurement speed is improved.

According to a second aspect of the present invention, in the coordinate measuring apparatus according to the first aspect, the comparator output is connected to the xL electrode or the xR electrode via a diode switch and a damping resistor, and a contact generated immediately after the start of keying. Damping is performed in an unstable region (high impedance region). Therefore, in addition to the effect of the coordinate measuring device of the first aspect, a stable area is provided at the time of keying detection, and keying detection measurement can be stabilized.

According to a third aspect of the present invention, in the coordinate measuring apparatus according to the first aspect, the comparator output is connected to the xL electrode or the xR electrode via a diode switch and a damping resistor, and the xL electrode or the key in the key pressed state is connected. By lowering the potential of the xR electrode, it can be separated from the threshold potential of the comparator. Therefore, in addition to the effect of the coordinate measuring device of the first aspect, the noise margin can be improved.

In the coordinate measuring apparatus for a touch panel according to the fourth aspect, keying detection → x coordinate measurement → y
Instead of the three steps of coordinate measurement, the x and y coordinates can be measured in two steps of y coordinate measurement (keystroke detection) → x coordinate measurement. Therefore, similarly to the coordinate measuring device of the first aspect, the measuring speed can be improved.

According to a fifth aspect of the present invention, in the coordinate measuring apparatus of the fourth aspect, damping is performed in a contact unstable area generated immediately after the start of keying. Therefore, in addition to the effect of the coordinate measuring device according to the fourth aspect, a stable area is provided at the time of keying detection, and keying detection measurement can be stabilized.

According to a sixth aspect of the present invention, in the coordinate measuring apparatus of the fourth aspect, the comparator output is connected to the yU electrode or the yL electrode via a diode switch and a damping resistor, and the yU electrode or the yU electrode in a key-pressed state is connected. By lowering the potential of the yL electrode, the potential of the yL electrode can be separated from the threshold potential of the comparator. Therefore, in addition to the effect of the coordinate measuring device according to the fourth aspect, the noise margin can be improved.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an example of an embodiment of a keying position detecting circuit for detecting a keying position of a touch panel in a coordinate measuring device according to the present invention.

FIG. 2 is a perspective view showing an example of a schematic structure of a conventional analog touch panel.

FIG. 3 is a schematic side view illustrating a deformation state of the touch panel shown in FIG. 2 during operation.

FIG. 4 is a functional block diagram illustrating an example of a keying position detection circuit that detects a keying position on the touch panel illustrated in FIG. 2;

[Explanation of symbols]

IC1 and IC2: Voltage follower, IC3: Comparator, IC4: A / D converter, LPF1 and LP
F2: Low-pass filter, ASW1 to ASW4: Analog switch, D1 to D3: Diode, R1 to R
8 ... resistor, C1 and C2 ... capacitor

Claims (6)

[Claims] 1. A substrate, one or both of which are opposed to each other, a flexible substrate, a conductive film having a finite electric resistance formed inside the substrate, and an end of each of the conductive films. And two sets of touch panel electrodes xL and xR and touch panel electrodes yU and yL, which are orthogonal to each other,
A touch panel comprising an insulating spacer between the two base materials, wherein two sets of electrodes xL, xR and electrodes yU,
A coordinate measuring apparatus comprising: a circuit switching means for switching a circuit of yL; and a comparator whose output is inverted by a predetermined threshold value, wherein a key tapping wait state is also used as an x coordinate measurement state. 2. The coordinate measuring device according to claim 1, wherein the comparator output is connected to a touch panel electrode xL or an electrode xR via a diode switch and a damping resistor to stabilize a keying detection characteristic. measuring device. 3. The coordinate measuring apparatus according to claim 1, wherein the comparator output is connected to the touch panel electrode xL or xR via a diode switch and a damping resistor, and the potential of the electrode xL or xR is reduced, thereby reducing the potential of the electrode xL or xR. A coordinate measuring device having an improved noise margin with respect to a threshold value of a comparator. 4. A substrate, one or both of which are opposed to each other, a flexible substrate, a conductive film having a finite electric resistance formed inside the substrate, and an end of each of the conductive films And two sets of touch panel electrodes xL and xR and touch panel electrodes yU and yL, which are orthogonal to each other,
A touch panel comprising an insulating spacer between the two base materials, wherein two sets of electrodes xL, xR and electrodes yU,
A coordinate measuring apparatus comprising: a circuit switching means for switching a circuit of yL; and a comparator whose output is inverted by a predetermined threshold value, wherein a key tapping wait state is also used as a y coordinate measurement state. 5. The coordinate measuring device according to claim 4, wherein the comparator output is connected to a touch panel electrode yU or an electrode yL via a diode switch and a damping resistor to stabilize a keying detection characteristic. . 6. The coordinate measuring device according to claim 4, wherein the comparator output is connected to a touch panel electrode yU or an electrode yL via a diode switch and a damping resistor, and the potential of the electrode yU or the electrode yL is reduced, whereby the potential of the electrode yU or the electrode yL is reduced. A coordinate measuring device having an improved noise margin with respect to a threshold value of a comparator.